"Behavior" pane

Active Edges: Select which edges of the screen can trigger a new shelf. Only the currently available edges are shown, according to the position of the Dock. If you uncheck all edges, you can still create new shelves by the New Shelf commands in the main menu.

Minimize inactive shelves: Set whether shelves should automatically minimize when you are not using them. See: The shelf. (Default: On)

Retain contents after dragging out: Set whether the shelf should close after you drag its contents out. Default is to automatically close. (Default: Off)